Strip seals, also known as feather seals, can be used to eliminate leakage flow between two components arranged adjacently to one another. This is achieved by the two components having groove recesses in edge faces that lie substantially opposite and adjacent one another. The strip seal seals the gap between the two components by being at least partially received into the groove recesses of the adjacently fitted components so as to span the gap between the components. U.S. Pat. No. 5,531,457 discloses an example of such a strip seal used to reduce leakage flow through the gap between two platforms of a blade.
The grooved recesses of fitted components often do not perfectly align due to, for example, manufacturing tolerances or as a result of thermal expansion. If the strip seal is manufactured so as to tightly fit into the groove recesses, less than perfect groove recess align would result in high stress loading of the strip seal, which can result in premature failure.
To overcome this problem strip seals can be made thinner than the height of the grooved recesses and flexible orthogonal to the strip seal length. In operation the pressure differential across the seal, due to the flexibility of the strip seal, forces the strip seal against one surface of the grooved recess so by effecting the seal. When the pressure differential is low strip seals are made thinner so as to increase their flexibility strip. To hold thin seals in place, for example during installation, the strip seal may be provided with biasing means, dispersed along the strip seal length. An example of biasing means in described in U.S. Pat. No. 3,836,279.
During operation the strip seals are exposed to periodic pressure pulsations caused by various rotating components within the gas turbine such as blades as they pass through rotating and non-rotating regions where the strip seals are contained within. These strip seals are generally placed in components like rotor blades, rotor heat shields or vane platforms and stators. The strip seals fit into the grooved recesses of components, providing a sealing between two portions of the components. A first portion faces low pressure from the hot gases, while second portion faces high pressure circulating in the gas turbine.
Depending on the strength and frequencies of the pressure pulsations, parts of the strip seal that are not biased against faces of the grooved recess or otherwise retained can be induced into periodic resonance leading to premature fatigue failure of the strip seal. This problem is particularly relevant in the sealing of components where rotating blades of the gas turbine induce pressure pulsation at sealing faces.
To overcome this problem, some strip seals designs have an arrangement of clamping projections along the length of the strip seal to suppress the damages caused due to pressure pulsations. However, these clamping projections are often worn out, as a relatively small surface area of these clamping projections makes contact with the grooved recesses of the components that are subjected to high oscillations and vibrations. There is therefore a need for a strip seal design that is resilient to fatigue failure and resonance induced by pressure pulsations caused by rotating and non-rotating components of a gas turbine.